By the USGS Appalachian Basin Province Assessment Team: Catherine B. Enomoto, Michael H. Trippi, Debra K. Higley, William A. Rouse, Frank T. Dulong, Timothy R. Klett, Tracey J. Mercier, Michael E. Brownfield, Heidi M. Leathers-Miller, Thomas M. Finn, Kristen R. Marra, Phuong A. Le, Cheryl A. Woodall and Christopher J. Schenk
In 2017, the U.S. Geological Survey completed a geology-based assessment of undiscovered, technically recoverable continuous (unconventional) natural gas in Upper Devonian shales of the Appalachian Basin: a mean of 10.7 trillion cubic feet.
The three assessed units — Cleveland, Huron and Rhinestreet — within the Devonian Shale–Middle and Upper Paleozoic Total Petroleum System. USGS.
What was assessed
The shales studied:
- the Cleveland and Huron Members of the Ohio Shale;
- the Pipe Creek Shale Member of the Java Formation;
- the Rhinestreet Shale Member of the West Falls Formation;
- the Middlesex Shale Member of the Sonyea Formation.
They lie beneath parts of Kentucky, New York, Ohio, Pennsylvania, Tennessee, Virginia and West Virginia.
The geologic model
The assessment rests on the elements of the Devonian Shale–Middle and Upper Paleozoic Total Petroleum System:
- source rocks — how rich they are, how mature, and how much oil and gas they made and held;
- reservoir — continuous shale, its extent and properties: minerals, porosity, permeability, brittleness;
- reservoirs and seals — their types, extent, and timing relative to generation.
The shales are mostly organic-rich marine shales, and their gas is considered self-sourced, largely because of their thermal maturity where they produce.
Eight units, three assessed. The USGS defined eight continuous assessment units (AUs) and estimated resources for three. Although some oil has come from the Ohio Shale and its Huron Member, the team concluded that future production will be mostly gas and natural gas liquids. The other five — Pipe Creek gas and oil, Rhinestreet oil, and Middlesex gas and oil — were left hypothetical, for lack of data.
| AU | Covers |
|---|---|
| Cleveland Continuous Gas | the Cleveland Member where it joins the Chattanooga Shale units assessed in 2015 (Higley and others, 2016); downdip of where Tmax — the temperature of peak hydrocarbon release in Rock-Eval pyrolysis (Espitalie and others, 1985) — reaches 435 °C; and all areas of past production from the member |
| Huron Continuous Gas | the same tests for the Huron Member |
| Rhinestreet Continuous Gas | the Rhinestreet Member downdip of the 1.2 percent vitrinite reflectance contour (East and others, 2012), and all areas of past production from it |
The estimates
For the three units, mean estimates:
- Gas: 10,657 billion cubic feet — about 10.7 trillion cubic feet (F95–F5 range 1,472 to 29,352).
- Natural gas liquids: 279 million barrels (33 to 811).
F95 means a 95-percent chance of at least that much; F5, a 5-percent chance.
| AU | Gas, mean (billion cubic feet) | Gas, F95–F5 | NGL, mean (million barrels) |
|---|---|---|---|
| Huron | 7,096 | 907–20,238 | 214 |
| Cleveland | 1,991 | 214–5,592 | 47 |
| Rhinestreet | 1,570 | 351–3,522 | 18 |
More: USGS Energy Resources Program.
Sources
Based on Assessment of Undiscovered Continuous Gas Resources in Upper Devonian Shales of the Appalachian Basin Province, 2017, by the Appalachian Basin Province Assessment Team, USGS Fact Sheet 2018–3018, U.S. Geological Survey; a work of the United States government in the public domain. The map is taken from the fact sheet's PDF, which the import had left out.
Licence: CC0 1.0 (public domain) · Adapted from pubs.usgs.gov
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